It is already known from British Pat. No. 1,197,322 to prepare a solution of cellulose in a mixture comprising dimethylformamide in the presence of an amine and sulphur dioxide, in which solution part of the dimethylformamide can be replaced by dimethyl sulphoxide, and to mix it with a solution of polyvinyl chloride in dimethylformamide. The British patent teaches that polyvinyl chloride is insoluble in dimethyl sulphoxide. Generally the starting cellulose solution contains one part by weight of cellulose for at least each four parts by weight of the dimethyl sulphoxide or other organic solvent, such as acetonitrile or dimethylformamide. At least 2.5 moles each of sulphur dioxide and the amine are used per mole of anhydroglucose unit of the cellulose. The patent does not teach the production of filaments or the spinning of the described cellulose/polyvinyl chloride solutions. In any event, however, the concentrations used (4% in the case of cellulose solution and 2% in the case of the polyvinyl chloride solution) are too low to permit the manufacture of fibres with good properties.
Commonly assigned U.S. Pat. No. 4,129,640 discloses a process for producing shaped articles of cellulose, wherein a shapable solution of cellulose in DMSO and formaldehyde, containing at least 6% by weight of cellulose, and having a weight ratio of formaldehyde/cellulose of about 0.2 to about 0.6, is contacted with a coagulating solution of DMSO and water at a temperature no greater than 10.degree. C. The coagulant bath contains 30-50% by weight of DMSO, with coagulation occurring generally in less than 20 seconds.
Commonly assigned U.S. Pat. No. 4,145,391 discloses a process for producing shaped cellulosic articles, wherein a solution of cellulose in DMSO and formaldehyde, at a formaldehyde/cellulose weight ratio of 0.2-2, and at a cellulose concentration of at least 6% by weight, is spun into a gaseous atmosphere containing ammonia.
Commonly assigned U.S. Pat. No. 4,173,613 is directed to a process for producing shaped cellulosic articles, wherein a solution of cellulose and DMSO and formaldehyde, at a formaldehyde/cellulose weight ratio of 0.2-2, and at a cellulose concentration of at least 6% by weight, is spun into a coagulant bath containing water, DMSO and ammonia or an ammonium salt.
Copending, commonly assigned application Ser. No. 147,221, filed May 6, 1980, now U.S. Pat. No. 4,377,648 issued Mar. 22, 1983 discloses shapable polymeric solutions containing cellulose having a degree of polymerisation of at least 200, an acrylonitrile polymer, dimethyl sulphoxide and formaldehyde, with the weight ratio of cellulose/acrylonitrile polymer being between 0.05 and 1, the weight ratio of formaldehyde/cellulose being between 0.2 and 2, and the total polymer concentration in the solution being between 12 and 30% by weight. The solutions may be extruded into a coagulating bath containing 25 to 80% by volume of water and 75 to 20% by weight of dimethyl sulphoxide, and maintained at a temperature of between 0.degree. and 40.degree. C., thereafter orientated, and at least substantially freed of solvent.
Copending, commonly assigned application Ser. No. 244,135, filed Mar. 16, 1981, now U.S. Pat. No. 4,363,895 issued Dec. 14, 1982, discloses shapable polymer solutions containing cellulose having a degree of polymerisation of at least 200, a polyamide-imide polymer, dimethyl sulphoxide and formaldehyde, with a weight ratio of cellulose/polyamide-imide being between 0.05 and 1, the weight ratio of formaldehyde/cellulose being between 0.2 and 2, and the total polymer concentration being between 6 and 25% by weight. These solutions may be spun into a coagulating bath containing water and 75 to 20% by volume of dimethyl sulphoxide, maintained at a temperature between 0.degree. and 40.degree. C., with the filaments being obtained orientated, freed of solvent, and overstretched at a temperature above 290.degree. C.